Synthesis of N-substituted quaternary carbon centers through KOt-Bu-catalyzed aza-Michael addition of pyrazoles to cyclic enones

Abstract

This study reports an efficient and mild method for the synthesis of cyclic β-amino ketones containing N-substituted quaternary carbon centers via the KOt-Bu-catalyzed aza-Michael addition reaction of pyrazoles to β-substituted cyclic α,β-enones. The amination was promoted by KOt-Bu (3 mol%) at ambient temperature and a wide range of new and versatile β-pyrazolyl ketones were obtained in good yields. Furthermore, the KOt-Bu-catalyzed one-pot diamination of a cyclic dienone with pyrazoles via an aza-1,6-conjugate addition followed by an aza-1,4-conjugate addition was also explored.